Root cause: Mediatek MT7921E Wi-Fi driver preventing suspend
Overview
Some Linux systems equipped with Mediatek MT7921/MT7922 Wi-Fi + Bluetooth cards fail to remain suspended.
When you attempt systemctl suspend, the machine briefly enters sleep and then instantly wakes back up.
Typical kernel logs show:
mt7921e 0000:05:00.0: PM: failed to suspend async: error -110
PM: Some devices failed to suspend, or early wake event detected
The mt7921e driver is known to hang during suspend, causing an “early wake”.
Additionally, missing Bluetooth firmware (BT_RAM_CODE_MT7922_1_1_hdr.bin) can trigger related messages.
Symptoms
- System resumes seconds after suspend.
- Journal entries include:
mt7921e ... failed to suspend async: error -110 PM: Some devices failed to suspend, or early wake event detected - Bluetooth firmware load errors:
bluetooth hci1: firmware: failed to load mediatek/BT_RAM_CODE_MT7922_1_1_hdr.bin
Root Cause
The mt7921e kernel module times out while entering the suspend state, preventing the system from completing S3 sleep.
As a result, the kernel aborts the suspend operation and immediately resumes power management — appearing as if the system “woke up by itself.”
Workaround: Unload the Driver Before Suspend
To allow clean suspend, the driver can be automatically unloaded before sleep and re-loaded after resume.
Step 1 – Create a systemd service
sudo tee /etc/systemd/system/mt7921e-sleep.service >/dev/null <<'EOF'
[Unit]
Description=Unload Mediatek mt7921e Wi-Fi before suspend and reload after resume
Before=sleep.target
StopWhenUnneeded=yes
[Service]
Type=oneshot
ExecStart=/usr/sbin/modprobe -r mt7921e
ExecStop=/usr/sbin/modprobe mt7921e
RemainAfterExit=yes
[Install]
WantedBy=sleep.target
EOF
Step 2 – Enable the service
sudo systemctl daemon-reload
sudo systemctl enable mt7921e-sleep.service
Step 3 – (Optional) Remove legacy hook script
If an old /etc/systemd/system-sleep/mt7921e.sh script exists, remove it:
sudo rm -f /etc/systemd/system-sleep/mt7921e.sh
sudo systemctl daemon-reload
Optional Improvements
Install Updated Firmware
Newer Mediatek firmware may resolve suspend issues:
sudo apt update
sudo apt install firmware-misc-nonfree
Disable Bluetooth (if unused)
echo "blacklist btusb" | sudo tee /etc/modprobe.d/blacklist-btusb.conf
Force Deep Sleep Mode
Ensure the kernel uses S3 “deep” instead of s2idle:
sudo sed -i 's/GRUB_CMDLINE_LINUX_DEFAULT="/GRUB_CMDLINE_LINUX_DEFAULT="mem_sleep_default=deep /' /etc/default/grub
sudo update-grub
Verification
After configuration:
systemctl suspend
- The system should remain suspended until you press a key or power button.
- On resume, verify in logs:
journalctl -u mt7921e-sleep.serviceYou should see:Started Unload Mediatek mt7921e Wi-Fi before suspend and reload after resume
Summary
| Component | Action |
|---|---|
| mt7921e Wi-Fi driver | Unload before suspend |
| Systemd integration | mt7921e-sleep.service |
| Old hook removal | Delete /etc/systemd/system-sleep/mt7921e.sh |
| Optional firmware | firmware-misc-nonfree package |
| Optional Bluetooth fix | Blacklist btusb if unused |
✅ Result: System now performs stable suspend-to-RAM.
Wi-Fi reconnects automatically on resume, and no further early-wake events appear in logs.